MILWAUKEE -- Well-rested Giants rookie pitcher Kyle Harrison was well on his way to providing a much-needed quality outing on Wednesday night against the Brewers. But a dramatic turn of events in the fifth inning soured his 23rd start of the season in San Francisco's 5-3 loss at American Family Field.

After having his last start skipped, Harrison was sharp early in his return to the mound in Milwaukee. He allowed a one-out single to Blake Perkins in the first, and then proceeded to retire eight in a row before walking Perkins in the fourth.

With the Giants and the Brewers locked in a scoreless battle, the 23-year-old lefty remained strong to start the fifth inning, striking out two of the first three batters while allowing a walk to light-hitting Andruw Monasterio.

Then trouble arrived -- in a hurry.

After walking No. 9 hitter Sal Frelick, Harrison surrendered a single to Jackson Chourio that plated the game’s first run. Perkins followed with a double to drive in two more before William Contreras crushed a two-run homer to put the Brewers in front 5-0 and chase Harrison.

“He pitched really well up to that point. He was getting strikeouts and swings and misses, throwing his breaking ball for a strike,” manager Bob Melvin said. “It just happened quickly on him. Shoot, I thought at the time that he might go six innings. They got three pretty good at-bats off him in a row, unfortunately, and it added up to five runs.”

An outing that started out so promising for Harrison (7-6) ended with this line: 4 2/3 innings pitched, four hits, five runs, three walks and seven strikeouts.

“I felt great today. Stuff was great,” Harrison said. “I think I got a little out of rhythm, didn’t get some calls my way. But I’ve got to look past that and get to the next pitch. I didn’t make as good of pitches as I’d like.”

The loss was a bitter one as the Giants try to stay in the Wild Card race. The defeat put them 6 1/2 games out of the final NL Wild Card berth.

“It’s frustrating. We want to come out with a win, especially going into the fifth with no runs [allowed],” Harrison said. “Just got to be better. I trusted my stuff but I got away from my stuff in that last inning. I wanted to stick with certain pitches and I gave in a little bit. You learn from that.”

It marked yet another outing where a Giants starter failed to get out of the fifth. In a three-game series last weekend in Seattle, Hayden Birdsong, Blake Snell and Robbie Ray each failed to complete five innings. In the series opener against the Brewers on Tuesday, Logan Webb made it to the sixth inning, but failed to retire a batter in the frame and departed after allowing a two-run homer to Willy Adames.

Harrison turned in a solid effort in his prior outing, allowing one run and five hits in six innings against the White Sox. The southpaw has pitched 121 2/3 innings this season, exceeding the 102 1/3 innings he threw between Triple-A Sacramento and the Giants last season.

San Francisco's offense, which accounted for three home runs in Tuesday's win, was held in check by Freddy Peralta, who threw six scoreless innings while allowing only two hits. Peralta struck out eight and walked three.

The Giants (67-67) finally got on the board in the seventh when Matt Chapman hit a leadoff double and later scored on Thairo Estrada’s infield single. The Giants cut the Brewers' lead to 5-3 in the eighth on Michael Conforto’s run-scoring double and an RBI single by Heliot Ramos.

“When you have a five-run inning, that can deflate you a little bit, but we came back against some really good bullpen arms and scored three runs and made it a game,” Melvin said.

But it was another contest where the Giants failed to score early.

“That’s the game of baseball,” Estrada said. “From the first inning on, we try to score early and make the job easier for our starting pitcher, but sometimes things don’t work out.”

Estrada addressed an earlier report by The Athletic that he and relievers Taylor Rogers and Tyler Matzek had been placed on waivers. The Giants have not officially confirmed the move.

“It happened once [to me]. I don’t think you ever get used to it,” Estrada said through a translator. “That’s something that I just can’t control. It’s part of the game. But the one thing I can control is just go out there again and play as hard as I can and try to get my team some wins.”

Estrada had two hits in four at-bats Wednesday night.